1. Field of the Invention
The present invention relates generally to an equipment for thermal stabilization process, and more particularly to an equipment for a thermal stabilization process of the photoresist pattern on the semiconductor wafer.
2. Description of Relevant Art
There are extensively produced semiconductor devices with high integrity, such as LSI's and VLSI's in recent years. Those devices are produced by repetition of a number of processes such as for the formation of an insulating or conductive film on the surface of a semiconductor wafer and for the etching of such a film. Exemplarily, in the case of an insulating film formed on a wafer, the etching includes a photo-lithographic process for forming a minute photoresist pattern on the insulating film, followed by a plasma etching process as a dry etching of the film, where the photoresist pattern serves as a mask.
The photoresist pattern formed by photo-lithography is insufficient of resistance to heat, and may deform if directly subjected to plasma, with a resulted difficulty in achieving a proper minute etching in the submicron order.
To overcome such a problem, there are conventionally known curing processes in which the photoresist pattern on the wafer is hardened by irradiation of ultraviolet ray.
For such a process, an equipment is proposed in Japanese Utility Model Laying-Open Gazette No. 61-97834. The equipment has a leftwardly and rightwardly openable cylindrical casing and a processing chamber installed therein, with a plurality of ultraviolet lamps verticalyy arranged therebetween. The processing chamber permits insertion of a cassette with many wafers piled to be held therein. Each lamp is provided with a transparent cover to allow circulation of cooling water through a space defined therebetween.
In the equipment, however, the cassette holds many wafers, so that the irradiation of ultraviolet ray thereto may be uneven. The photoresist pattern on each wafer may be cured ununiform in resistance to heat or thermal stability. It may thus be difficult to perform a correct etching.
It is desirable for improvement in thermal stability of photoresist to possibly eliminate residual moisture and solvent therein, in addition to curing by ultraviolet irradiation. Such elimination may be effected by heating the photoresist during the ultraviolet irradiation under a vacuum pressure. It however is difficult for the equipment according to the Japanese Gazette, in which many wafers are piled in the cassete, to concurrently perform both heating and ultraviolet irradiation under vacuum pressure, under given conditions.
The present invention has been achieved to effectively solve such a problem in conventional equipment for thermal stabilization process of photoresist pattern on semiconductor wafer.